1. Field
The presently disclosed subject matter relates to a vehicle supplemental restraint system (SRS) that includes a controller, such as a central processing unit, that is located away from positions either at the floor tunnel or underneath the instrument panel. In particular, the disclosed subject matter relates to an SRS in which controller(s) are installed at a vehicle frame's cross-member located underneath or to the rear of the driver, and SRS controllers and SRS devices that include built-in acceleration devices.
2. Brief Description of the Related Art
Many of today's vehicles have both frontal and side airbag systems as well as other supplemental active restraint structures that require quick and accurate judgment and activation. The SRS control unit acts as the brain to provide this quick and accurate control for the system, and any improvement in either speed or accuracy is a long felt need/desire for the SRS control unit art.
Typically, the control unit for an SRS is located in or on the floor tunnel underneath or behind the center counsel and/or underneath the instrument panel. In general, the control unit for an SRS is located towards the front of the vehicle. This position of the SRS control unit makes it difficult to determine certain events, such as a lower impulse crash located towards the rear of the vehicle. The current remedy for boosting the SRS control unit's ability to detect and evaluate such events is to provide additional satellite “g” sensors (in the form of accelerometers, etc.) which can either detect and send data back to the SRS control unit or act as a saving system.
The “g” sensors are devices that work with the control unit to discriminate between crash and non-crash events. These sensors measure the severity of the impact, and are set up so that sudden “negative acceleration” will cause contacts to close. A signal is then sent to the control unit which checks for a signal from various sensors (e.g., front sensor(s), rear sensor(s), side sensor(s), rollover sensor(s), etc.). Depending on the signal strength and sequence of activated sensors, the SRS control unit then determines which and how many airbags and/or other active restraints to deploy and at what level of power to deploy them.
By function, there are two main types of sensors: impact sensors and saving sensors. The front/forward sensors are typically impact sensors that are located in various areas forward of the passenger compartment. For example, the front/forward sensors can be located inside the fenders, on the front frame, etc. The front (and other) sensors can take the form of a typical accelerometers, or can be more advance and include several sensors bundled together. Two general types of accelerometers that can be used as a front/forward sensor include the ball and magnet type sensor and the spring band and roller type sensor. One more specific type of sensor is known as a variable reluctance (VR) speed and position sensor, which is widely used in the automotive industry because of its low cost and high reliability. Unlike other types of sensors, VR sensors are self-excited. They do not require an external voltage source to operate.
Rear sensors are sometimes known as saving sensors when they are only used to determine that a crash has actually occurred. Rear saving sensors can be located in various locations in the passenger compartment. Other saving sensors can actually be integrated with the SRS control unit itself.
Saving sensors, whose purpose is the prevention of malfunction, are incorporated into an SRS to detect an impact from collision simultaneously with the main acceleration sensor in the deployment of the airbag or other restraint. However, there are problems associated with the acceleration sensor for the side airbag or side crash activated devices. In a side collision the crushable zone is smaller than in a head-on collision, so in a side collision, the deployment of the airbag or other restraints must be quicker. Therefore, analog sensors are sometimes used for the side airbags because mechanical lead-switch type saving sensors, used mainly for front collision sensors, have a slow response speed. However, analog sensors can be relatively expensive and subject to electromagnetic disturbance.
The total severity of a vehicle crash cannot be determined until the crash event is complete. However, in certain applications, SRS control units may be required to discriminate the severity of the crash event in the first milliseconds of an impact. Future SRS control units may require even more discrimination capability than current systems to provide separate deployment thresholds for advanced technologies such as multi-staged airbags, pretensioners, and decision shifting for belted and unbelted occupants. Therefore there exists a long felt need to improve both the accuracy and speed of all components of an SRS, including processor speed/accuracy, communication speed/accuracy, sensor speed/accuracy, etc.